In ITS (Intelligent Transport Systems), road-vehicle-vehicle communication is studied in which information is exchanged between a road-side device and a vehicle or between vehicles by using an ad-hoc wireless network.
On the other hand, research into inter-vehicle communication that uses a mobile communication network [for example, 3G, LTE (Long Term Evolution)] has also been undertaken recently.
In order for a center to provide a mobile terminal, such as a cellular terminal (for example, a smart phone) or a dedicated onboard device and so on, with telematics services or road-vehicle-vehicle collaborative services (hereinafter referred to as “information notification services” collectively) which use location information of a vehicle transmitted via a mobile communication network, a location management server in the center needs to collect location information transmitted from mobile terminals via base stations.
However, transmitting location information at high frequency from a mobile terminal that is mounted on a vehicle, leads to an increase in traffic and to over use of the network bandwidth. Therefore, an improvement in the efficiency of the communication of the location information is required.
Patent Documents 1 and 2 describe an onboard communication device that dynamically changes a transmission interval of location information as necessary in order to improve the efficiency of the communication of the location information. The onboard communication device, which is described in Patent Document 1, shortens the transmission interval when a dangerous vehicle approaches. The onboard communication device, which is described in Patent Document 2, changes the transmission interval in accordance with the speed of the approaching vehicle.